Memory is one type of integrated circuitry, and is used in systems for storing data. Memory is usually fabricated in one or more arrays of individual memory cells. The memory cells are configured to retain or store information in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.
Integrated circuit fabrication continues to strive to produce smaller and denser integrated circuits. Accordingly, there has been substantial interest in memory cells that can be utilized in structures having programmable material between a pair of electrodes. Examples of such memory cells are resistive RAM (RRAM) cells, phase change RAM (PCRAM) cells, and programmable metallization cells (PMCs)—which may be alternatively referred to as a conductive bridging RAM (CBRAM) cells, nanobridge memory cells, or electrolyte memory cells. The memory cell types are not mutually exclusive. For example, RRAM may be considered to encompass PCRAM and PMCs.
The programmable materials have two or more selectable resistive states to enable storing of information. Programmable materials that are receiving increasing interest are multi-portion materials (which are sometimes referred to in the art as multi-layer materials). Example multi-portion programmable materials are materials containing at least two different oxide portions. Such materials may be programmed by moving oxygen species (for instance, oxygen ions) within and between the different portions. Other example multi-portion programmable materials are materials comprising an ion source region and a switching region. The ion source region may comprise, for example, a combination of copper and tellurium; and the switching region may comprise, for example, an oxide or solid state electrolyte.
The utilization of multi-portion programmable materials can provide advantages in nonvolatile memory applications. For instance, the multi-portion programmable materials may enable specific memory states to be tailored for particular applications. Although multi-portion programmable materials show promise for utilization in nonvolatile memory architectures, there remain challenges in incorporating such materials into integrated circuitry.